E-Beam vs. Gamma Sterilization E-Beam vs. Gamma

E-Beam vs. Gamma Sterilization
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APPLES n’ APPLES: Many of the sterilization issues concerning gamma and electron beam radiation
are the same; 1) the mechanism by which living organisms are destroyed is the same, 2) both enjoy
parametric release after processing, and 3) both utilize the same dosimetry and indicator systems. This
point is supported by the fact that both technologies are governed by the same ISO standards when
applied to medical device sterilization, ISO 11137 and ISO 13409. Both technologies have been proven
effective at sterilization and are accepted world wide.
APPLES n’ ORANGES: There are, however, significant differences between the two forms of
sterilization radiation processing. The medical device engineer or regulatory manager should
evaluate which method is right for the product(s) in question and for the future of their company.
Conversion from one technology to another is fairly straightforward and the guidelines for
validation of the changeover are found in the ISO standards mentioned above. The major differences between electron beam and
gamma irradiation are:
Penetration Gamma rays can penetrate
farther into materials, occasionally
colliding with an electron and giving the
affected electrons enough energy to
destroy the bioburden. The gamma ray
may then initiate more high energy
electrons as it travels through the medical device, see Fig 1. Electron beams start
out as very high energy electrons and
destroy bioburden directly. In addition,
these high energy electrons collide with
other local electrons. These secondary
electrons also have energy adequate to
destroy bioburden. This results in an increase in the dose as the beam penetrates the medical
device. Each succeeding collision reduces the energy of the resulting electrons until there is no
penetrating power left in the beam, see Fig. 2.
Dose Rate or Processing Time The
dose rate is the biggest difference
between the two technologies.
Gamma radiation has high penetration
and low dose rate. E-beam has high
dose rate and low penetration. Either
technology can give a reproducible
sterilization dose. Gamma radiation is
best suited to treating a large batch of
many “totes” of boxes over a 6-10 hour
cycle. E-beam is a continuous process
that can deliver a required dose in 1-2
minutes as individual boxes pass by the
e-beam accelerator. The lower “dwell time” in the E-beam irradiation process is less stressful to
materials. The E-beam process allows faster turnaround time and more flexibility in delivering a
specific irradiation dose to small batches of product. E-beam can easily switch from decontaminating returned goods at 40 kGy to sterilizing a batch of radiation sensitive product at 15 kGy.
Material Effects Much has been written about the effects of gamma and e-beam radiation on
plastic materials. The general consensus is that e-beam is more friendly to a plastic medical
device and its packaging than gamma. These differences are attributed to the longer dwell time
H15a E-Beam vs. Gamma Sterilization
Effective Date: 10/30/08
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in gamma irradiation cells during which ozone, other reactive compounds, and heat can accumulate. The short dwell time of E-beam has less severe effects on materials because the radiation
by-products rapidly dissipate after the short exposure to irradiation. NUTEK has several comprehensive references available to its customers that compare changes in yellowing, embrittlement
and strength characteristics when subject polymers are exposed to varying doses from both
forms of irradiation.
Environmental There are no direct environmental issues that affect the end users of contract
sterilizer services. The gamma irradiator must cope with higher containment and reprocessing
costs, however, that may be reflected in overall operating costs. With E-beam irradiation, when
the power is turned off, the radiation stops.
Costs Generally the per box rate for sterilization irradiation is less using gamma when large
batches of high density material are processed. However, the set-up costs and minimum fees for
E-beam are usually significantly lower. This means that E-beam tends to be advantageous for
small to midsize sterilization lots of medical devices. In addition, the quick turn around in
processing adds to the value of E-beam technology for the medical device manufacturer. Even
large lots may be more economically processed using E-beam if the final packaging is designed
to match the penetration power of the E-beam facility.